Which combination creates a tertiary color?

Mixing a secondary color with a primary color results in a tertiary color, which is why this choice is correct. Tertiary colors are created by combining one primary color with one of its adjacent secondary colors on the color wheel. For example, if you mix blue (a primary color) with green (a secondary color), you get cyan, which is classified as a tertiary color.

The other options focus on different combinations of colors. Mixing two primary colors yields a secondary color, while combining two secondary colors produces a different hue, but not a tertiary color. Mixing equal parts of black and white simply results in a shade of gray, which does not pertain to the creation of a tertiary color.